The present invention relates generally to the miniaturized liquid phase sample processing and analysis. More particularly, the invention relates to a miniaturized planar separation device with a means of delivering sample constituents to a mass spectrometer (MS).
Sensitive identification of analytes in a complex sample matrix is difficult, and requires careful thought as to (a) the preparation of the sample for MS analysis (i.e., detergents, buffer salts, etc.), (b) whether a separation step is required to simplify the complexity of the sample for MS analysis, and (c) whether additional sample processing (i.e., chemical, enzymatic, affinity capture, etc.) is required to generate the desired information from the MS analysis of the sample. An ideal device would allow rapid detection of a wide range of simple or complex molecules in the liquid phase, at relevant concentrations, and yield information about the molecule""s molecular mass. Additional chemical structural information may be gained by employing a tandem MS technique, such as, but not necessarily limited to Quadrupole Time-of-Flight tandem MS or Ion Trap MS. A desirable feature of the detection method would be to enable the separation criteria to be relaxed such that the separation and detection could occur in series, without the need for high-efficiency, high-end separation technology, such as standard high performance liquid chromatography equipment. The orthogonality of MS analysis to liquid-based separation techniques helps make this possible. An on-line detector is particularly advantageous when sample size is limited, high throughput is required, and automation is desired. Moreover, MS detection methods are well suited to yield high quality chemical information for multi-component samples, requiring no a priori knowledge of the constituents.
Though much has been discussed in the literature towards realizing integrated separation technology including sample preparation and separation devices, and associated fluidics so that low yield or precious samples may be prepared and analyzed, little has been realized to date. In sample analysis instrumentation, particularly in separation systems involving capillary electrophoresis or liquid chromatography, smaller dimensions of the separation compartments result in improved performance characteristics, while reducing cost of analysis and production. Miniaturization of the separation region, to result in small sample volume requirements, necessarily means a greater demand on the detection method both by virtue of sample volume and potentially, sensitivity.
There are many types of detection methods possible. Optical transmission methods such as refractive index, ultraviolet-visible (UV-VIS) and infrared (IR) are relatively inexpensive, but are unable to give complex chemical structural information. Furthermore, they are path-length limited and sensitivity of detection is limited. Infrared spectroscopy is relatively insensitive, particularly to contaminants, and yields only functional group or fingerprint identification. MS is a sensitive method providing mass information and tandem MS can provide detailed structural information.
The sensitivity of analysis with conventional separation methods for on-line mass spectrometric detection typically suffers from adsorptive sample loses and from sample contamination during sample handling procedures. The development of microfluidic devices for separation coupled with delivery to an electrospray ionization mass spectrometer holds the promise to greatly increase analysis sensitivity by minimizing the complexity of the interface by incorporating features such as make-up flow elements, on-device metallization, and on-device fluidic interconnect features that readily allow for zero dead-volume incorporation of make-up flow elements or MS transfer lines. Additionally, higher sample throughputs are possible, as the scale of any microfluidic device is much smaller, and consequently faster, than currently existing conventional-scale fluidic devices.
The present invention relates to a miniaturized planar device, which can be used in a liquid phase analysis system. It is a primary object of the invention to provide a miniaturized device that has been microfabricated in a substantially planar substrate. The analytical device generally has at least one separation component, which is adapted for a direct, on-line coupling to an associated mass spectrometer.
In one embodiment of the invention, a miniaturized device is provided. The device comprises (a) a substrate having first and second substantially planar opposing surfaces and lateral surfaces substantially perpendicular to the planar surfaces, wherein the substrate has a first microchannel having an interior surface and a second microchannel having an interior surface in the first planar surface, (b) a cover plate arranged over the first planar surface having first and second substantially planar opposing surfaces and lateral end surfaces substantially perpendicular to the planar surfaces, wherein (i) the first surface of the cover plate in combination with the first microchannel forms a separation compartment having first and second termini and (ii) the first surface of the cover plate in combination with the second microchannel forms a channel compartment having first and second termini, and further wherein the second terminus of the separation compartment and the first terminus of the channel compartment are coterminus, (c) an inlet port in fluid communication with the first terminus of the first microchannel and a make-up flow port in fluid communication with the second terminus of the first microchannel, respectively, wherein the inlet port enables the passage of fluid from a first source through the separation compartment, and the make-up flow port enables the passage of fluid from a second source through a make-up flow channel in fluid communication the second terminus of the separation compartment and a channel compartment having first and second termini, wherein the first terminus of the channel compartment is in fluid communication with the second terminus of the separation compartment and second terminus of the channel compartment is in fluid communication with an on-device mass spectrometer delivery means.
These and other embodiments of the subject invention will readily occur to those of ordinary skill in the art in view of the disclosure herein.